If you have it on at all, active or not, DO NOT attempt to connect to Zombie Mode or Multiplayer, even if it's to download a map, weapons, whatever. They will detect the trainer, and you will be banned. I've used it with Single Player multiple times with no ill effects, however. If you plan to connect to Zombie or Multiplayer after you finish playing around with Single Player, make sure to close out the game completely first.

---------------------------------------------------------------------------Kill a thousand men and they will hate you. Kill a million men and they will queue to face you. But kill a single man and they will see monsters and devils in every shadow.